"A Magical Kingdom" triggers when you enter Kiddie Kingdom. A layer of radioactive mist hangs in the air, and a mysterious voice on the PA system taunts you. Suit up in your power armor or bring a decent supply of Rad-X and Rad-Away. You will have to search three areas in the park to progress the quest.
Search the tunnels
The entrance to the employees' tunnels is accessible through the Nuka-Racers tunnels. Follow the track and cars as they cross the moat on the right side of the castle. You'll briefly meet Oswald Outrageous before he vanishes in a puff of smoke.
Search the fun house
Head to the fun house. Make your way through the maze of mirrors. The last obstacle of the maze is a large conveyor belt. Sprint to get across it, but be wary of the grenade bouquet waiting for you at the end.
Your next challenge is a set of rotating platforms that require you to jump across. Ghouls infest the water, and you must cross the platforms to progress. The hole in the wall at the bottom leads to a door that cannot be unlocked.
The hypnotic halls are up next. To reduce nausea, hack the terminal before you head in. The last tunnel has large cutouts, be careful not to fall or you'll have to backtrack.
The Escher room has no real dangers.
The last room has a spinning floor and 11 doors. All are amusing to check out, but the notable ones are, going clockwise from the one you start from:
- Red door 2: a radioactive room with a hidden Cappy and a Nuka-Cade ticket roll
- Red door 4: the exit
Both doors are pictured above.
Search the theater
The theater is in King Cola's Castle. Cross the moat, enter the grounds of the castle, and prepare to fight a lot of ghouls. Oswald will make an appearance and disappear once more. Head backstage for some loot including a roll of Nuka-Cade tickets in the control room on the upper level of the theater.
The order you search the three areas doesn't matter.
Upon the third, Oswald will taunt you and demand that you meet him on the roof of King Cola's Castle for a showdown. Take the elevator that in the theater's backstage.
You can kill him or convince him to leave through difficult persuasion checks. If you've found Rachel's holotape in the King Cola Castle tower, you can use that to persuade him as well.
To complete the quest, assign a gang using the signal flagpole on the balcony of the roof.
Completing the quest and leaving the quest area will activate a miscellaneous objective. Travel back to claim your gang's tribute stash.